'''common.py: common classes for ufw'''
#
# Copyright 2008-2018 Canonical Ltd.
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License version 3,
#    as published by the Free Software Foundation.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
#

import re
import socket
import ufw.util
from ufw.util import debug

programName = "ufw"
state_dir = "/lib/ufw"
share_dir = "/usr/share/ufw"
trans_dir = share_dir
config_dir = "/etc"
prefix_dir = "/usr"
iptables_dir = "/usr/sbin"
do_checks = True


class UFWError(Exception):
    '''This class represents ufw exceptions'''
    def __init__(self, value):
        self.value = value

    def __str__(self):
        return repr(self.value)


class UFWRule:
    '''This class represents firewall rules'''
    def __init__(self, action, protocol, dport="any", dst="0.0.0.0/0",
                 sport="any", src="0.0.0.0/0", direction="in", forward=False,
                 comment=""):
        # Be sure to update dup_rule accordingly...
        self.remove = False
        self.updated = False
        self.v6 = False
        self.dst = ""
        self.src = ""
        self.dport = ""
        self.sport = ""
        self.protocol = ""
        self.multi = False
        self.dapp = ""
        self.sapp = ""
        self.action = ""
        self.position = 0
        self.logtype = ""
        self.interface_in = ""
        self.interface_out = ""
        self.direction = ""
        self.forward = forward
        self.comment = ""
        try:
            self.set_action(action)
            self.set_protocol(protocol)
            self.set_port(dport)
            self.set_port(sport, "src")
            self.set_src(src)
            self.set_dst(dst)
            self.set_direction(direction)
            self.set_comment(comment)
        except UFWError:
            raise

    def __str__(self):
        return self.format_rule()

    def _get_attrib(self):
        '''Print rule to stdout'''
        res = "'%s'" % (self)
        keys = list(self.__dict__)
        keys.sort()
        for k in keys:
            res += ", %s=%s" % (k, self.__dict__[k])
        return res

    def dup_rule(self):
        '''Return a duplicate of a rule'''
        rule = UFWRule(self.action, self.protocol)
        rule.remove = self.remove
        rule.updated = self.updated
        rule.v6 = self.v6
        rule.dst = self.dst
        rule.src = self.src
        rule.dport = self.dport
        rule.sport = self.sport
        rule.multi = self.multi
        rule.dapp = self.dapp
        rule.sapp = self.sapp
        rule.position = self.position
        rule.logtype = self.logtype
        rule.interface_in = self.interface_in
        rule.interface_out = self.interface_out
        rule.direction = self.direction
        rule.forward = self.forward
        rule.comment = self.comment

        return rule

    def format_rule(self):
        '''Format rule for later parsing'''
        rule_str = ""

        if self.interface_in != "":
            rule_str += " -i %s" % (self.interface_in)
        if self.interface_out != "":
            rule_str += " -o %s" % (self.interface_out)

        # Protocol is handled below
        if self.protocol == "any":
            rule_str += " -p all"
        else:
            rule_str += " -p " + self.protocol

            if self.multi:
                rule_str += " -m multiport"
                if self.dport != "any" and self.sport != "any":
                    rule_str += " --dports " + self.dport
                    rule_str += " -m multiport"
                    rule_str += " --sports " + self.sport
                elif self.dport != "any":
                    rule_str += " --dports " + self.dport
                elif self.sport != "any":
                    rule_str += " --sports " + self.sport

        if self.dst != "0.0.0.0/0" and self.dst != "::/0":
            rule_str += " -d " + self.dst
        if not self.multi and self.dport != "any":
            rule_str += " --dport " + self.dport
        if self.src != "0.0.0.0/0" and self.src != "::/0":
            rule_str += " -s " + self.src
        if not self.multi and self.sport != "any":
            rule_str += " --sport " + self.sport

        lstr = ""
        if self.logtype != "":
            lstr = "_" + self.logtype
        if self.action == "allow":
            rule_str += " -j ACCEPT%s" % (lstr)
        elif self.action == "reject":
            rule_str += " -j REJECT%s" % (lstr)
            if self.protocol == "tcp":
                # follow TCP's default and send RST
                rule_str += " --reject-with tcp-reset"
        elif self.action == "limit":
            # Caller needs to change this
            rule_str += " -j LIMIT%s" % (lstr)
        else:
            rule_str += " -j DROP%s" % (lstr)

        if self.dapp != "" or self.sapp != "":
            # Format the comment string, and quote it just in case
            comment = "-m comment --comment '"
            pat_space = re.compile(' ')
            if self.dapp != "":
                comment += "dapp_" + pat_space.sub('%20', self.dapp)
            if self.dapp != "" and self.sapp != "":
                comment += ","
            if self.sapp != "":
                comment += "sapp_" + pat_space.sub('%20', self.sapp)
            comment += "'"

            rule_str += " " + comment

        return rule_str.strip()

    def set_action(self, action):
        '''Sets action of the rule'''
        tmp = action.lower().split('_')
        if tmp[0] == "allow" or tmp[0] == "reject" or tmp[0] == "limit":
            self.action = tmp[0]
        else:
            self.action = "deny"

        logtype = ""
        if len(tmp) > 1:
            logtype = tmp[1]
        self.set_logtype(logtype)

    def set_port(self, port, loc="dst"):
        '''Sets port and location (destination or source) of the rule'''
        err_msg = _("Bad port '%s'") % (port)
        if port == "any":
            pass
        elif loc == "dst" and self.dapp:
            pass
        elif loc == "src" and self.sapp:
            pass
        elif re.match(r'^[,:]', port) or re.match(r'[,:]$', port):
            raise UFWError(err_msg)
        elif (port.count(',') + port.count(':')) > 14:
            # Limitation of iptables
            raise UFWError(err_msg)
        else:
            ports = port.split(',')
            if len(ports) > 1:
                self.multi = True

            tmp = ""
            for p in ports:
                if re.match(r'^\d+:\d+$', p):
                    # Port range
                    self.multi = True
                    ran = p.split(':')
                    for q in ran:
                        if int(q) < 1 or int(q) > 65535:
                            raise UFWError(err_msg)
                    if int(ran[0]) >= int(ran[1]):
                        raise UFWError(err_msg)
                elif re.match('^\d+$', p):
                    if int(p) < 1 or int(p) > 65535:
                        raise UFWError(err_msg)
                elif re.match(r'^\w[\w\-]+', p):
                    try:
                        p = socket.getservbyname(p)
                    except Exception:
                        raise UFWError(err_msg)
                else:
                    raise UFWError(err_msg)

                if tmp:
                    tmp += "," + str(p)
                else:
                    tmp = str(p)

            port = tmp

        if loc == "src":
            self.sport = str(port)
        else:
            self.dport = str(port)

    def set_protocol(self, protocol):
        '''Sets protocol of the rule'''
        if protocol in ufw.util.supported_protocols + ['any']:
            self.protocol = protocol
        else:
            err_msg = _("Unsupported protocol '%s'") % (protocol)
            raise UFWError(err_msg)

    def _fix_anywhere(self):
        '''Adjusts src and dst based on v6'''
        if self.v6:
            if self.dst and (self.dst == "any" or self.dst == "0.0.0.0/0"):
                self.dst = "::/0"
            if self.src and (self.src == "any" or self.src == "0.0.0.0/0"):
                self.src = "::/0"
        else:
            if self.dst and (self.dst == "any" or self.dst == "::/0"):
                self.dst = "0.0.0.0/0"
            if self.src and (self.src == "any" or self.src == "::/0"):
                self.src = "0.0.0.0/0"

    def set_v6(self, v6):
        '''Sets whether this is ipv6 rule, and adjusts src and dst
           accordingly.
        '''
        self.v6 = v6
        self._fix_anywhere()

    def set_src(self, addr):
        '''Sets source address of rule'''
        tmp = addr.lower()

        if tmp != "any" and not ufw.util.valid_address(tmp, "any"):
            err_msg = _("Bad source address")
            raise UFWError(err_msg)
        self.src = tmp
        self._fix_anywhere()

    def set_dst(self, addr):
        '''Sets destination address of rule'''
        tmp = addr.lower()

        if tmp != "any" and not ufw.util.valid_address(tmp, "any"):
            err_msg = _("Bad destination address")
            raise UFWError(err_msg)
        self.dst = tmp
        self._fix_anywhere()

    def set_interface(self, if_type, name):
        '''Sets an interface for rule'''
        # libxtables/xtables.c xtables_parse_interface() specifies
        # - < 16
        # - not empty
        # - doesn't contain ' '
        # - doesn't contain '/'
        #
        # net/core/dev.c from the kernel specifies:
        # - < 16
        # - not empty
        # - != '.' or '..'
        # - doesn't contain '/', ':' or whitespace
        if if_type != "in" and if_type != "out":
            err_msg = _("Bad interface type")
            raise UFWError(err_msg)

        # Separate a few of the invalid checks out so we can give a nice error
        if '!' in str(name):
            err_msg = _("Bad interface name: reserved character: '!'")
            raise UFWError(err_msg)

        if ':' in str(name):
            err_msg = _("Bad interface name: can't use interface aliases")
            raise UFWError(err_msg)

        if str(name) == "." or str(name) == "..":
            err_msg = _("Bad interface name: can't use '.' or '..'")
            raise UFWError(err_msg)

        if (len(str(name)) == 0):
            err_msg = _("Bad interface name: interface name is empty")
            raise UFWError(err_msg)

        if (len(str(name)) > 15):
            err_msg = _("Bad interface name: interface name too long")
            raise UFWError(err_msg)

        # We are going to limit this even further to avoid shell meta
        if not re.match(r'^[a-zA-Z0-9_\-\.\+,=%@]+$', str(name)):
            err_msg = _("Bad interface name")
            raise UFWError(err_msg)

        if if_type == "in":
            self.interface_in = name
        else:
            self.interface_out = name

    def set_position(self, num):
        '''Sets the position of the rule'''
        # -1 prepend
        #  0 append
        # >0 insert
        if str(num) != "-1" and not re.match(r'^[0-9]+', str(num)):
            err_msg = _("Insert position '%s' is not a valid position") % (num)
            raise UFWError(err_msg)
        self.position = int(num)

    def set_logtype(self, logtype):
        '''Sets logtype of the rule'''
        if logtype.lower() == "log" or logtype.lower() == "log-all" or \
           logtype == "":
            self.logtype = logtype.lower()
        else:
            err_msg = _("Invalid log type '%s'") % (logtype)
            raise UFWError(err_msg)

    def set_direction(self, direction):
        '''Sets direction of the rule'''
        if direction == "in" or direction == "out":
            self.direction = direction
        else:
            err_msg = _("Unsupported direction '%s'") % (direction)
            raise UFWError(err_msg)

    def get_comment(self):
        '''Get decoded comment of the rule'''
        return ufw.util.hex_decode(self.comment)

    def set_comment(self, comment):
        '''Sets comment of the rule'''
        self.comment = comment

    def normalize(self):
        '''Normalize src and dst to standard form'''
        changed = False
        if self.src:
            try:
                (self.src, changed) = ufw.util.normalize_address(self.src, \
                                                                 self.v6)
            except Exception:
                err_msg = _("Could not normalize source address")
                raise UFWError(err_msg)

            if changed:
                self.updated = changed

        if self.dst:
            try:
                (self.dst, changed) = ufw.util.normalize_address(self.dst, \
                                                                   self.v6)
            except Exception:
                err_msg = _("Could not normalize destination address")
                raise UFWError(err_msg)

            if changed:
                self.updated = changed

        if self.dport:
            ports = self.dport.split(',')
            ufw.util.human_sort(ports)
            self.dport = ','.join(ports)

        if self.sport:
            ports = self.sport.split(',')
            ufw.util.human_sort(ports)
            self.sport = ','.join(ports)

    def match(x, y):
        '''Check if rules match
        Return codes:
          0  match
          1  no match
         -1  match all but action, log-type and/or comment
         -2  match all but comment
        '''
        if not x or not y:
            raise ValueError()

        dbg_msg = "No match '%s' '%s'" % (x, y)
        if x.dport != y.dport:
            debug(dbg_msg)
            return 1
        if x.sport != y.sport:
            debug(dbg_msg)
            return 1
        if x.protocol != y.protocol:
            debug(dbg_msg)
            return 1
        if x.src != y.src:
            debug(dbg_msg)
            return 1
        if x.dst != y.dst:
            debug(dbg_msg)
            return 1
        if x.v6 != y.v6:
            debug(dbg_msg)
            return 1
        if x.dapp != y.dapp:
            debug(dbg_msg)
            return 1
        if x.sapp != y.sapp:
            debug(dbg_msg)
            return 1
        if x.interface_in != y.interface_in:
            debug(dbg_msg)
            return 1
        if x.interface_out != y.interface_out:
            debug(dbg_msg)
            return 1
        if x.direction != y.direction:
            debug(dbg_msg)
            return 1
        if x.forward != y.forward:
            debug(dbg_msg)
            return 1
        if x.action == y.action and x.logtype == y.logtype and \
                x.comment == y.comment:
            dbg_msg = _("Found exact match")
            debug(dbg_msg)
            return 0
        if x.action == y.action and x.logtype == y.logtype and \
                x.comment != y.comment:
            dbg_msg = _("Found exact match, excepting comment")
            debug(dbg_msg)
            return -2

        dbg_msg = _("Found non-action/non-logtype/comment match " \
                    "(%(xa)s/%(ya)s/'%(xc)s' %(xl)s/%(yl)s/'%(yc)s')") % \
                    ({'xa': x.action, 'ya': y.action,
                      'xl': x.logtype, 'yl': y.logtype,
                      'xc': x.comment, 'yc': y.comment})
        debug(dbg_msg)
        return -1

    def fuzzy_dst_match(x, y):
        '''This will match if x is more specific than y. Eg, for protocol if x
           is tcp and y is all or for address if y is a network and x is a
           subset of y (where x is either an address or network). Returns:

            0  match
            1  no match
           -1  fuzzy match

           This is a fuzzy destination match, so source ports or addresses
           are not considered, and (currently) only incoming.
        '''
        def _match_ports(test_p, to_match):
            '''Returns True if p is an exact match or within a multi rule'''
            if ',' in test_p or ':' in test_p:
                if test_p == to_match:
                    return True
                return False

            for port in to_match.split(','):
                if test_p == port:
                    return True
                if ':' in port:
                    (low, high) = port.split(':')
                    if int(test_p) >= int(low) and int(test_p) <= int(high):
                        return True

            return False

        if not x or not y:
            raise ValueError()

        # Ok if exact match
        if x.match(y) == 0:
            return 0

        dbg_msg = "No fuzzy match '%s (v6=%s)' '%s (v6=%s)'" % \
                   (x, x.v6, y, y.v6)

        # Direction must match
        if y.direction != "in":
            debug("(direction) " + dbg_msg + " (not incoming)")
            return 1

        # forward must match
        if y.forward != x.forward:
            debug(dbg_msg + " (forward does not match)")
            return 1

        # Protocols must match or y 'any'
        if x.protocol != y.protocol and y.protocol != "any":
            debug("(protocol) " + dbg_msg)
            return 1

        # Destination ports must match or y 'any'
        if y.dport != "any" and not _match_ports(x.dport, y.dport):
            debug("(dport) " + dbg_msg)
            return 1

        if y.interface_in == "":
            # If destination interface is not specified, destination addresses
            # must match or x must be contained in y

            if x.interface_in == "" and x._is_anywhere(x.dst):
                # if x and y interfaces are not specified, and x.dst is
                # anywhere then ok
                pass
            elif x.dst != y.dst and '/' not in y.dst:
                debug("(dst) " + dbg_msg)
                return 1
            elif x.dst != y.dst and '/' in y.dst and x.v6 == y.v6 and \
               not ufw.util.in_network(x.dst, y.dst, x.v6):
                debug("(dst) " + dbg_msg + " ('%s' not in network '%s')" % \
                      (x.dst, y.dst))
                return 1
        else:
            # If destination interface is specified, then:
            #  if specified, both interfaces must match or
            #  the IP of the interface must match the IP of y or
            #  the IP of the interface must be contained in y
            if x.interface_in != "" and x.interface_in != y.interface_in:
                debug("(interface) " + dbg_msg + " (%s != %s)" % \
                      (x.interface_in, y.interface_in))
                return 1

            try:
                if_ip = ufw.util.get_ip_from_if(y.interface_in, x.v6)
            except IOError:
                debug("(interface) " + dbg_msg + " %s does not exist" % \
                      (y.interface_in))
                return 1

            if y.dst != if_ip and '/' not in y.dst:
                debug("(interface) " + dbg_msg + " (%s != %s)" % \
                      (y.dst, if_ip))
                return 1
            elif y.dst != if_ip and '/' in y.dst and x.v6 == y.v6 and \
               not ufw.util.in_network(if_ip, y.dst, x.v6):
                debug("(interface) " + dbg_msg + \
                      " ('%s' not in network '%s')" % (if_ip, y.dst))
                return 1

        if x.v6 != y.v6:
            debug("(v6) " + dbg_msg + " (%s != %s)" % (x.dst, y.dst))
            return 1

        # if we made it here, it is a fuzzy match
        debug("(fuzzy match) '%s (v6=%s)' '%s (v6=%s)'" % (x, x.v6, y, y.v6))
        return -1

    def _is_anywhere(self, addr):
        '''Check if address is anywhere'''
        if addr == "::/0" or addr == "0.0.0.0/0":
            return True
        return False

    def get_app_tuple(self):
        '''Returns a tuple to identify an app rule. Tuple is:
             dapp dst sapp src direction_iface|direction
           or
             dport dst sapp src direction_iface|direction
           or
             dapp dst sport src direction_iface|direction

           where direction_iface is of form 'in_eth0', 'out_eth0' or
           'in_eth0 out_eth0' (ie, both interfaces used). If no interfaces are
           specified, then tuple ends with the direction instead.
        '''
        tupl = ""
        if self.dapp != "" or self.sapp != "":
            tupl = "%s %s %s %s" % (self.dapp, self.dst, self.sapp, self.src)
            if self.dapp == "":
                tupl = "%s %s %s %s" % (self.dport, self.dst, self.sapp, \
                                         self.src)
            if self.sapp == "":
                tupl = "%s %s %s %s" % (self.dapp, self.dst, self.sport, \
                                         self.src)

            # if neither interface exists, add the direction
            if self.interface_in == "" and self.interface_out == "":
                tupl += " %s" % (self.direction)
            # otherwise, add the interfaces
            else:
                if self.interface_in != "":
                    tupl += " in_%s" % (self.interface_in)
                if self.interface_out != "":
                    tupl += " out_%s" % (self.interface_out)

        return tupl

    def verify(self, rule_iptype):
        '''Verify rule'''
        # Verify protocol not specified with application rule
        if self.protocol != "any" and \
           (self.sapp != "" or self.dapp != ""):
            err_msg = _("Improper rule syntax ('%s' specified with app rule)") \
                        % (self.protocol)
            raise UFWError(err_msg)

        if self.protocol in ufw.util.ipv4_only_protocols and \
           rule_iptype == "v6":
            # Can't use protocol these protocols with v6 addresses
            err_msg = _("Invalid IPv6 address with protocol '%s'") % \
                        (self.protocol)
            raise UFWError(err_msg)

        if self.protocol in ufw.util.portless_protocols:
            if self.dport != "any" or self.sport != "any":
                err_msg = _("Invalid port with protocol '%s'") % \
                            (self.protocol)
                raise UFWError(err_msg)